The present invention is directed to the field of tubular accordion filter elements. Such elements are used, for example, to remove dust from air. The filters separate a clean-air region from a dust-laden air region. To this end, they are mounted on a carrier, to which they must be tightly joined.
German patent 34 39 194 discloses a tubular accordion filter element having at its ends flexible end plates, made of plastic molding compound, which form a truncated cone and are mounted in an annular shape around the filter element. The contact surface formed by the truncated cone extends to the filter element.
Furthermore, it is known from the German laid open publication 44 41 508 to seal off the end faces of the filter element with an elastic substance. This has the disadvantage that a mold is necessary for the elastic substance, as the filter element must be dipped into the mold and remain there until the elastic substance hardens. From EP-OS 0 724 472, an end piece is known made of irregularly placed fibers embedded in synthetic resin. In this case, one end of the filter is hermetically sealed.
An object of the present invention is to form the end pieces of an accordion filter element in a manner allowing their cost-effective production. Another object is to permit the securement of the accordion filter element to the carrier structure, which also provides a sealing function.
The present invention provides for the end piece to have on a radially exterior side niece a transition area, in the area of which adjacent to the end face of the end piece, the accordion filter element has a bulge, adjoined by a necking which extends away from the end face. This in turn is followed by a straight or frustoconical area.
A method for producing a tubular accordion filter element is also taught. A tubular filter body is embedded at the extremity into a molding compound and provided with a U-shaped end piece, by pouring the molding compound in the liquefied state into a U-shaped groove open parallel to the filter axis, the filter body subsequently being introduced into the groove and being partially immersed in the molding compound, and remaining there to produce a permanent bond.